1. Field of the Invention
The present invention relates to a gas turbine and a gas turbine cooling method.
2. Description of the Related Art
In a gas turbine, air is compressed by a compressor and fuel is added to the compressed air to produce an air-fuel mixture. The air-fuel mixture is burnt and resulting high-temperature, high-pressure combustion gases are used to drive the turbine. Thermal efficiency of an overall gas turbine plant can be increased by combining it with another plant, such as a steam turbine. Meanwhile, in a recent gas turbine, a pressure ratio of the combustion gases has been increased with intent to increase the thermal efficiency by using the gas turbine alone. For that reason, the differential pressure across each turbine blade provided in a gas path in a turbine section has been increased in comparison with that in the past. This gives rise to the necessity of reducing the amount of sealing air leaked through gaps between adjacent parts. In order to prevent the combustion gases from flowing into the inside of a turbine rotor, for example, the sealing air supplied to a wheel space on the upstream side must be prevented from leaking to a wheel space on the downstream side through a gap between the turbine rotor as a rotating member and a nozzle vane as a stationary member. To that end, a diaphragm is engaged with a lower portion of the nozzle vane.
For the purpose of holding air tightness of a cavity defined by the nozzle vane and the diaphragm, JP-B-62-37204 discloses a structure in which prestress is applied to a foot end of the diaphragm (i.e., a diaphragm hook) such that the diaphragm hook comes into pressure contact with a nozzle vane hook.